I haven't played a lot of games, and never in a tournament.
I play against friends so we don't have a great experience in term of rules.
But I have tried shielding recently, and it helped me a lot. Actually, I feel more confortable on the table since I do it
A point about might : I still have fear to use it to call heroic combats (what if I loose? It's a wasted point / Is it a good idea to call an heroic combat there? What would I do next? / ...).
Concerning deployment, I still have some troubles in doing it in "the most efficient way" (cavalry, for instance). But I use my bowmen better than I used to (and I don't fear to send them into melee when I judge that it's time :p)
I alors have learnt some tips by reading/watching battle reports : how do other people play, what kind of strategy do they use, ... I remember that I have sometimes said "Wait, what? Is it legal?" and checked the rulebook to confirm it... It was really helpul